System and method for intensity modulated radiation therapy

Abstract

A dynamic IMRT scheme. A RAD ON/RAD OFF cycle is an IMRT segment. Every set of opposing leaves in the collimator produces an IMRT profile or track. According to such an embodiment, at least one of the opposing leaves moves toward the other to produce the given track. When a track is complete, the opposing leaves remain together until the end of the segment. The dose rate remains constant during the segment.

What is claimed is:  
     
       1. A method for delivering radiation therapy, comprising: 
       defining a RAD on/RAD OFF cycle as an IMRT segment;  
       defining sets of opposing leaves as an IMRT profile;  
       moving at least one of said opposing leaves toward the other to produce a track;  
       maintaining a constant dose rate during the segment; and  
       wherein every moving leaf goes from an open position to a closed position.  
     
     
       2. A method according to  claim 1 , wherein when a track is closed, the opposing leaves remain closed until the end of the segment. 
     
     
       3. A method according to  claim 2 , wherein selecting a leaf velocity profile and dose rate comprises: 
       finding a minimum slope within a given segment;  
       selecting a maximum leaf speed and calculating a corresponding dose rate;  
       if the dose rate is within range, determining a speed corresponding to a maximum slope and verifying that it is within range;  
       if the dose rate is outside the range, reducing the speed a predetermined increment and determining again if the dose rate is within range;  
       once dose rate and maximum speed are within range, calculating a minimum speed; and  
       if minimum speed is within range, then determining all leaf speed profiles.  
     
     
       4. A radiation therapy device, comprising: 
       a linear accelerator;  
       a beam shielding device including at least one pair of opposing leaves, said at least one pair defining a track during a treatment segment; and  
       a controller adapted to determine a leaf speed profile for a segment such that at least one of said opposing leaves constantly moves toward the other from an open position to a closed position on said track while dose rate remains constant during the segment.  
     
     
       5. A device according to  claim 4 , said beam shielding device comprising a multi-leaf collimator. 
     
     
       6. A device according to  claim 5  wherein, when a track is complete the corresponding leaves remain closed until the end of the segment. 
     
     
       7. A device according to  claim 6 , said controller is adapted to determine a leaf speed profile by determining a minimum slope; 
       calculating a dose rate if a maximum leaf speed is used;  
       determining a speed corresponding to a maximum slope if dose rate is within a predetermined range;  
       calculating a minimum speed; and  
       calculating all leaf profiles.  
     
     
       8. A radiation therapy device according to  claim 6 , determining leaf profiles, said leaf profiles constrained by a system minimum and maximum speed and maximum dose rate. 
     
     
       9. A radiation therapy device, comprising: 
       means for delivering radiation to a body;  
       a multileaf collimator comprising a plurality of sets of opposing leaves, said sets defining tracks; and  
       a controller operable to control said multileaf collimator and said radiation delivering means such that at least one of the opposing leaves constantly moves toward the other from an open position to a closed position on a track while dose rate remains constant during a segment.  
     
     
       10. A radiation therapy device in accordance with  claim 9 , wherein when a track is complete the corresponding leaves remain closed until the end of the segment. 
     
     
       11. A controller for a radiation therapy device, the device including a multileaf collimator having a plurality of sets of opposing leaves, the sets defining tracks, the controller adapted to control said device such that at least one of the opposing leaves constantly moves toward the other from an open position to a closed position on a track while dose rate remains constant during a segment. 
     
     
       12. A controller in accordance with  claim 11 , wherein when a track is complete the corresponding leaves remain closed until the end of the segment.